Blackboard-eraser.



T. H. COSTELLO.

BLAOKBOARD ERASER.

APPLICATION FILED JULY 23, 1909.

1,089,047. Patented Mar.3,1914.

COLUMBIA PLANDGRAPH co, WASHINGTON, n. c.

I f l S v OFFTCE.

BLAGKBOARD-ERASER.

Specification of Letters Patent.

Patented Mar. 3, 1914.

Application filed July 23, 1909. Serial No. 509,158.

T 0 all whom it may concern:

Be it known that I, THOMAS H. GosrELLo, a citizen of the United States, residing at the city of Chicago, in the county of Cook and State of Illinois, have invented a new and useful Improvement in Blackboard- Erasers, of which the following is a specification.

My invention relates to erasers for blackboards and similar use. These are usually provided with felt rubbing faces secured to a back of more or less flexible material, and attachment between the face pieces and the back is commonly made by a layer of glue or cement. The latter is hard and unyielding, and when the rubbing face is worn down by continued use, the eXposed portions of glue or cement frequently scratch and disfigure the blackboard.

My invention provides a means by which the parts of the device are securely attached to each other; the rubbing face may be worn completely to the back without disclosing the attaching cement, and the back may be made firm and rigid while the faces are so bedded therein as to make a firm, symmetrical and finished product.

The principles of my invention are illustrated in the drawings, in which like characters of reference denote like parts throughout.

Figure l is a perspective view of an eraser made according to the principles of my invention; Fig. 2 is a cross section thereof on the line 22 of Fig. 1; Fig. 3 is a View of the underside of the back before the rubbing pieces are attached.

Further describing my invention: 1 represents a piece of felt of proper form, usually rectangular, having a depressed portion 2, leaving the raised rim 3. This conformation should be of permanent character and is best produced by placing a layer of sizing material over the portion to be depressed, said sizing being sufliciently fluid to cause it to penetrate some distance into the fibers of the felt. The sized portion should then be compressed and left under pressure long enough to allow it to set. When sufliciently dried or hardened the rubbing pieces a should have their upper edges secured within the said depressed portion of the back by a layer of glue or cement which should be confined to the bottom of the depression 2. It will thus be seen that the entire body of the rubbing material formed from the strips t may be worn away down to the face of the rim 3, and even below, without permitting the blackboard to be injured by abrasion from the adhesive material used.

I claim:

A blackboard eraser comprising a back of elastic fibrous material having its inner face depressed except at the marginal edges, the marginal edges forming a projecting ridge entirely around the depressed portion of the inner face, a rubbing body formed of the same material as the back and comprising a plurality of rectangular strips of less length than the back and having their side faces abut-ting and unattached throughout and further having their inner longitudinal edges received in the depressed face of the back and completely filling the space inclosed by the projecting ridge, and a layer of cement securing said edges to the back, said cement layer being removed from the outer edge of the ridge.

In witness whereof, I have hereunto set my hand this 8th day of July 1909, in the presence of two subscribing witnesses.

T. H. COSTELLO.

Vitnesses:

C. K. CHAMBERLAIN, A. S. PHILLIPS.

topics 0! this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. G. 

